Mobile Push Booking Alerts

I need a small, dependable solution that watches a specific website’s booking flow and immediately triggers mobile-app push notifications whenever a new slot, confirmation, or status change appears. Email or SMS are not required; push notifications are the sole channel. I don’t need a full-blown dashboard—basic, hard-coded configuration is fine as long as I can adjust the key parameters in a file or a few constants.

Core expectations
• Monitoring logic that reliably detects the booking events I will specify (e.g., page change, API response, or DOM element update).
• A lightweight back-end or background script that pushes the alert through a standard mobile push service (Firebase Cloud Messaging or an equally straightforward alternative).
• Clear setup instructions so I can deploy it on my own server and link the push service to my existing mobile app.
• A quick walkthrough or short screen-share proof that the notification fires when a test booking action is performed.

Keep the code tidy, well commented, and limited to the essentials—no interface work is needed.